The present invention relates to a rod-like probe for the capacitive measurement of the level in a container, the probe forming the one electrode and the container the other electrode of a capacitor whose capacitance depends on the level in the container.
Rod-like probes of this type are used either for continuous level measurement, then extending substantially over the entire height of the container and consequently having a considerable length, or for determining when certain limit levels are reached, when they may be shorter. In both cases the problem is encountered that a breakage or tearing away of the probe is difficult to detect and leads to erroneous indication of the level.
The objective of the present invention is to provide a rod-like probe of the type mentioned at the beginning which permits reliable detection of probe detachment or breaking away.
According to the invention this is achieved in that the probe includes two electrical conductors insulated from each other which are electrically connected together at the ends facing the container interior and the ends of which remote from the container interior are provided with electrical terminals separate from each other.
In the rod-like probe according to the invention the two terminals of the probe conductors for the capacitance measurement, which is carried out with high-frequency alternating current, are at the same potential so that the inductance of the loop is of no consequence. The probe behaves like a simple rod. However, the loop existing between the two terminals affords the possibility of checking the satisfactory direct electrical connection between the two terminals during operation. When the probe is broken away this electrical direct connection is interrupted so that the check reliably detects the fault.